1. Field of the Invention
The present invention relates to a novel hard coat film, more particularly a hard coat film having excellent resistance to impact and weather, and suitable for being stuck on external surfaces, in particular those of window panes and plastic boards for windows.
2. Description of the Prior Art
It is known to apply plastic films on window panes and plastic boards for windows for various purposes. For example, sunlight entering a room through a window pane contains ultraviolet and infrared rays, in addition to visible rays. The ultraviolet rays in sunlight causes sunburn. Its adverse effects on a human body have been recently pointed out, and it is well known that it deteriorates a packing material and content thereof. The infrared rays in sunlight, on the other hand, increase temperature in a room by direct sunlight, lowering an air-conditioning effect in summer. In order to avoid these undesirable effects, window panes and plastic boards for windows are covered with an ultraviolet- or infrared-shielding film. They are also frequently covered with a film for view-obstructing purposes, or for preventing fragment scattering when the window pane is broken by a hazard, e.g., earthquake. The above films for shielding ultraviolet or infrared rays, or for view obstruction also have an effect of preventing fragment scattering.
More recently, use of the above-described plastic films has been studied, to protect window panes of vehicles running at a high speed. For example, a train generates a high wind pressure when it is passing through a tunnel, thus blowing off pebbles and snow blocks which may directly attack the train""s window panes. The plastic film for preventing the above troubles is especially required to be high resistant to impact, and also to be highly resistant to weather because it is put in service continuously under severe conditions.
A film to be stuck on window panes or plastic boards for windows (hereinafter sometimes referred to as a window film) is generally coated with a hard coat layer, such as that of ionization radiation-curable resin (e.g., polyester acrylate-, epoxy acrylate-, urethane acrylate- and polyol acrylate-based resin), coated and cured thereon, to provide the film having resistance to scratching. Incorporation of an ultraviolet scattering agent in the hard coat layer to provide resistance to weather may deteriorate the resistance of the hard coat surface to scratching. Incorporation of an ultraviolet absorber, on the other hand, may prevent curing by ionization radiation or deteriorate the resistance to scratching. It is therefore very hard for conventional hard coat films to provide a base film having a satisfactory effect of shielding ultraviolet rays. It is therefore generally stuck on an inner surface of the window pane or the like, because, when stuck on an outer surface, it may extensively deteriorate the hard coat layer and base film with ultraviolet rays, and contaminate the surface, to greatly decrease a film service life.
The hard coat film to be stuck on an inner surface is unsuitable as a wind film for the above-mentioned vehicles running at a high speed, because windows are directly attached by pebbles or snow blocks and their external surfaces must be protected.
Therefore, a hard coat film high in surface hardness, and excellent in resistance to impact and weather has been increasingly in demand, in particular for outdoor window films.
Japanese Patent Laid-Open No. 309813/1999 discloses a xe2x80x9chard coat film comprising a transparent base film coated, on its one side, with hard coat layers of an ultraviolet-shielding layer and a hard coat layer comprising silicon compound containing the siloxane bond in this order.xe2x80x9d Although this publication teaches that base film may be laminated film, examples thereof merely teach the single-layer base film. The hard coat film with the single-layer film as the base may not sufficiently protect glass, although preventing scattering of glass fragments, depending on degree of impact loaded thereon.
In order to solve the above problems, the present invention provides a preferably transparent hard coat film having excellent resistance to impact and weather and high surface hardness, which is particularly suitable for application, as by sticking on external surfaces, such as, for example, on window panes or plastic boards for windows.
The hard coat film of the present invention is characterized by comprising a silicone-based hard coat layer provided on one side of a multi-layered base composed of a plurality of the same or different resin films laminated.
The multi-layered base for the present invention may be a multi-layered film composed of a plurality of the same resin films laminated or a multi-layered film composed of a plurality of different films laminated.
In particular, when the multi-layered film composed of a plurality of different resin films laminated is used, it preferably contains a weather-resistant resin film and a impact-resistant resin film. In such a case, it is particularly preferable that the silicone-based hard coat layer is provided on the weather-resistant resin film.
The weather-resistant resin film is preferably of a resin film or a polycarbonate or polymethyl methacrylate film containing an ultraviolet absorber, of which a polycarbonate or polymethyl methacrylate film containing an ultraviolet absorber is more preferable.
The hard coat film of the present invention is suitably used by sticking the hard coat film on the external surfaces, e.g., those of window panes and plastic boards for windows.
The hard coat film of the present invention, having the above-mentioned unique structure, is resistant to impact and weather, high in surface hardness, and in particular suitable for application on external surfaces of window panes or plastic boards for windows.
The hard coat film of the present invention, having the above-mentioned unique structure, is resistant to impact and weather, high in surface hardness, and in particular suitable for being stuck on the external surfaces, e.g., those of window panes or plastic boards for windows.